Field monitoring of natural pipeflow over the last two decades has demonstrated its potential importance both as a hillslope drainage process and as a source of streamflow, yet very few attempts have been made to model the process. The main model designed to simulate pipeflow to date is shown to be unrepresentative of the natural field situation. This paper describes a semi-distributed simulation model with physically based parameters that has been designed around the field situation, as monitored in the longest run field experiment on pipeflow. The results are encouraging, despite the fact that data on a number of relevant parameters can be difficult to obtain at less intensely studied field sites.